The overnight cultures were diluted into 50 mL of medium to an OD600 nm of 0.05 and grown for several hours to an OD600 nm of 0.2. To determine the relative amounts of glutathionylspermidine and of spermidine in each strain, cells were prelabeled with 1.25 μCi of [14C]-spermidine trihydrochloride (12.5 nmoles), and the incubation was continued for either 2 h (‘log-phase culture’ OD600 nm = 0.7) or 20 h (‘overgrown culture’). The cultures were rapidly centrifuged at room temperature. The pellets were washed

twice with medium and re-suspended in 10% perchloric acid (1 : 5 wt/vol); the supernatants were subjected to HPLC chromatography on a Shim-pack cation exchange selleck products column with the elution system described in the previous section but with 1.0 M NaCl-0.2 M MLN0128 sodium citrate as the elution buffer. The elutes were collected at 2-min intervals (0.7 mL min−1), and a 100-μL aliquot from each fraction was counted in a Beckman scintillation counter (LS6500). Three independent cultures (109–1010 cells) from the E. coli gss+ and Δgss cells (OD600 nm of 0.7–0.8) were

harvested and re-suspended in Tris-EDTA buffer (100 mM Tris, 10 mM EDTA, pH 8.0) containing 2 mg mL−1 lysozyme (Sigma). The cell suspensions were incubated for 5 min at room temperature to digest the cell wall. Total RNA was isolated according to the protocol described in the RNeasy mini kit (Qiagen, Germantown, MD). The mRNAs were enriched from total RNA by removing the 16S and 23S ribosomal RNAs using the MICROBExpress method and kit (part no. AM1905; Ambion). The quantity and quality of RNA were evaluated by OD260 nm/OD280 nm assays and by RNA capillary electrophoresis (Agilent Biotechnologies). Enriched mRNAs were reverse-transcribed by Superscript II and random hexanucleotide primer

(Invitrogen) and used for microarrays as described earlier (Chattopadhyay et al., 2009a) using Affymetrix (Santa Clara, CA) E. coli GeneChip arrays (Genome 2.0 array; n = 3 each for gss+ and Δgss). anova (analysis of variance) was performed, and P-values were calculated Tideglusib using Partek Pro-software (Partek, St. Louis, MO) and plotted in negative log scale on y-axis against the Affimetrix signal ratios for each probe set on x-axis. Up- and down-regulated genes were selected based on P-values of <0.05 and fold change > +2 or −2. The complete microarray data can be obtained from GEO (accession number GSE30679). Most striking is that sequences homologous to E. coli Gss are only found in Eubacteria and the very distantly related Kinetoplastids (plus two fungal species with relatively low homology; Table 2). No homologous sequences (as defined by the blast-p program) were found when the E. coli Gss sequence was compared with the human, rat, mouse, Arabidopsis, rice, worm, and Drosophila sequence databases (Table 2).